COLUMBUS, Ohio (AP) — An environmental group seeking documents related to alleged illegal dumping of wastewater from oil and gas drilling into a northeast Ohio storm sewer is suing the state for access to the records.

The Sierra Club filed its suit Monday in the Ohio Supreme Court. The group alleges the Ohio Department of Natural Resources has not produced records responsive to a public records request sent six months ago.

The club's Ohio chapter is seeking documents related to the department's investigation of D&L Energy and Hardrock Excavating in Youngstown.

The department revoked the firms' permits in February amid a federal investigation into the dumping of up to 40,000 gallons of wastewater from hydraulic fracturing into a storm sewer that drains into the Mahoning River.